Revisited Kata: Using Midje's defrecord-openly to mock a protocol in Ohce

Several weeks ago I did the Ohce kata in Clojure using outside-in TDD with Midje (as I explained in a previous post).

In that post I said that I hadn't used Midje's defrecord-openly and provided macros and had instead decided to write my own code to capture the arguments with which the functions of the Notifier protocol implementation were being called because:

... I didn't like having to use defrecord-openly in production code.

Well, I was wrong!

It turns out that it is not necessary at all to use defrecord-openly in your production code in order to mock a protocol.

I understood it thanks to this answer in Stak Overflow: Mocking Clojure protocols.

The only thing I needed to do was to use defrecord-openly to create a fake implementation of the Notifier protocol inside the test code like this:

	(unfinished greet)
	(unfinished echo)
	(unfinished palindromes-rock)
	(unfinished bye-user)
	(defrecord-openly FakeNotifier []
	notifications/Notifier
	(greet [this greeting])
	(echo [this reversed-phrase])
	(palindromes-rock [this])
	(bye-user [this name]))

view raw fake-notifier-using-defrecord-openly.clj hosted with ❤ by GitHub

and then write the tests against this unimplemented fake.

This are the new Ohce tests:

	(ns ohce.unit-tests.ohce-test
	(:require
	[midje.sweet :refer :all]
	[ohce.ohce :refer :all]
	[ohce.notifications :as notifications]
	[midje.open-protocols :refer [defrecord-openly]]))
	(unfinished select-greeting)
	(unfinished read-input)
	(unfinished greet)
	(unfinished echo)
	(unfinished palindromes-rock)
	(unfinished bye-user)
	(defrecord-openly FakeNotifier []
	notifications/Notifier
	(greet [this greeting])
	(echo [this reversed-phrase])
	(palindromes-rock [this])
	(bye-user [this name]))
	(facts
	"about ohce"
	(fact
	"it greets the user"
	(let [notifier (->FakeNotifier)
	stop-word "Stop!"]
	(ohce select-greeting notifier read-input stop-word ...username...) => irrelevant
	(provided
	(read-input) => "Stop!"
	(select-greeting ...username...) => ...greeting...
	(greet notifier ...greeting...) => irrelevant :times 1)))
	(fact
	"it reverses the user inputs"
	(let [notifier (->FakeNotifier)
	stop-word "Stop!"]
	(ohce select-greeting notifier read-input stop-word ...username...) => irrelevant
	(provided
	(select-greeting ...username...) => irrelevant
	(read-input) =streams=> ["hola" "lolo" "Stop!"]
	(echo notifier "aloh") => irrelevant :times 1
	(echo notifier "olol") => irrelevant :times 1)))
	(fact
	"it ignores inputs that are blank"
	(let [notifier (->FakeNotifier)
	stop-word "Stop!"]
	(ohce select-greeting notifier read-input stop-word ...username...) => irrelevant
	(provided
	(select-greeting ...username...) => irrelevant
	(read-input) =streams=> ["memo" "" "moko" "Stop!"]
	(echo notifier "omem") => irrelevant :times 1
	(echo notifier "okom") => irrelevant :times 1)))
	(fact
	"it identifies palindromes"
	(let [notifier (->FakeNotifier)
	stop-word "Stop!"]
	(ohce select-greeting notifier read-input stop-word ...username...) => irrelevant
	(provided
	(select-greeting ...username...) => irrelevant
	(read-input) =streams=> ["oto" "ana" "Stop!"]
	(echo notifier "oto") => irrelevant :times 1
	(echo notifier "ana") => irrelevant :times 1
	(palindromes-rock notifier) => irrelevant :times 2)))
	(fact
	"it knows when to stop"
	(let [notifier (->FakeNotifier)
	stop-word "Stop!"]
	(ohce select-greeting notifier read-input stop-word ...username...) => irrelevant
	(provided
	(select-greeting ...username...) => irrelevant
	(read-input) =streams=> ["Stop!"]
	(bye-user notifier ...username...) => irrelevant :times 1))))

view raw ohce_test_properly_using_defrecord-openly.clj hosted with ❤ by GitHub

As you can see it's very easy to use Midje's defrecord-openly to mock protocols.

I just misunderstood Midje's documentation the first time I tried to do it...